Ingestible capsules are well-known in the prior art. Such capsules are generally small pill-like devices that can be ingested or swallowed by a patient. It is known that such capsules may include one or more sensors for determining physiological parameters of the gastrointestinal tract, such as sensors for detecting temperature, pH and pressure.
A number of methods of determining location of an ingestible capsule are known in the prior art. For example, it is known that signal strength or signal triangulation may be used to attempt to determine the location of an ingested capsule. However, the use of an RF signal has a number of disadvantages, including that it generally requires multiple antennas, various tissues may impact the signal differently, and patient movement may skew the results. It is also known that accelerometers may be used to attempt to determine location, but such methods also have disadvantages, such as drift, non-linear progression and rotational inaccuracy.
It is also known that certain physiological parameters may be associated with regions of the gastrointestinal tract. For example, a 1988 article entitled “Measurement of Gastrointestinal pH Profiles in Normal Ambulant Human Subjects” discloses pH measurements recorded by a capsule passing through the gastrointestinal tract. It is known that pH has been correlated with transitions from the stomach to the small bowel (gastric emptying) and from the distal small bowel to the colon (ileo-caecal) junction.